The power dissipated in a resistor can be written as
Correct answer: A. I squared R, VI, or V squared over R
- A. I squared R, VI, or V squared over R
- B. IR only
- C. V squared R
- D. I over R
Explanation
All three forms follow from P equals VI combined with Ohm's law, and which one is most convenient depends on what the question gives you. Use I squared R when the current is fixed, as in a series circuit, and V squared over R when the voltage is fixed, as in parallel household wiring. Note that for fixed voltage a smaller resistance dissipates more power, which surprises many students.
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About Maximum Power Output
Maximum power output describes the condition in which a source with internal resistance delivers the greatest power to an external load. The topic uses P = I²R and related circuit equations to show that maximum power occurs when load resistance equals internal resistance. This differs from maximum efficiency, which occurs under a separate condition.
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